This invention relates to prostaglandin synthesis. The synthesis of prostaglandins E.sub.1, E.sub.2, F.sub.1.sub..alpha., and F.sub.2.sub..alpha. in optically active form constituted notable achievements (E. J. Corey, et al., J. Amer. Chem. Soc. 92:397, 1970; 42:2586, 1970; and earlier papers). These synthetic sequences are particularly characterized by mild and specific reaction conditions. Further progress in prostaglandin research was severely encumbered by the lack of a stereoselective means for the introduction of the chiral (asymmetric) carbon which bears the sidechain secondary alcohol function of the prostaglandins (C-15). This chiral center is labelled in the formula below for prostaglandin E.sub.1. ##SPC1##
In the published procedure (E. J. Corey, et al., J. Amer. Chem. Soc. 91:5675, 1969) using zinc borohydride as the reducing agent, a 1:1 mixture of epimers is obtained when Ketone I (a trans-3-enone lactone) is reduced to the corresponding trans-3-enol (Alcohol II and III). Only one of these epimers (Alcohol II), which is the S-configuration isomer, is suitable for conversion to natural prostaglandins. ##SPC2##